In the art of vehicle navigation, typically a planned route is obtained by performing route finding; once the planned route is obtained, route guidance along the planned route is provided in order to guide a driver of the vehicle from a current position to the destination of the planned route. The route guidance, in other words, is provided to assist the driver in following the planned route by taking appropriate driving actions.
In the context of route guiding, special attention is being paid to turning events, i.e., positions along the planned route where the driver can chose between a plurality of paths to continue. In order to ensure that the driver follows the planned route, it is particularly relevant to provide the route guidance at such turning events. This enables the driver to take the particular driving action which allows to follow the planned route.
A typical turning event is an intersection. An intersection is generally defined as a road junction where two or more roads meet or cross. Typically, at an intersection, the driver of the vehicle has a plurality of driving choices and the route guidance along the planned route supports the driver in taking the particular driving action which follows along the planned route.
A database typically stores map data of a road network which comprises a plurality of road segments. The end points of neighbouring road segments are connected by nodes. A series of road segments may form a road. Sometimes the road network is formally described by means of a road network graph comprising the road segments and the nodes connecting the road segments as edges and vertices. In such a scenario, an intersection may be described as a node associated with more than two road segments. Such a road network graph enables to perform route finding algorithms, e.g., the Dijkstra algorithm and variations thereof, as part of the route finding.
Conventionally, the road network graph is employed not only for the route finding, but additionally for the route guidance: the route guidance along the planned route at an intersection typically includes displaying turning indicators in a map view. Such a turning indicator may include one or more arrows which are arranged along the participating road segments. In such a scenario it may be possible to calculate the turn indicators for the route guidance along the planned route at run-time, e.g., based on the road segments and nodes of the road network graph. There may be no need to store additional data for providing the route guidance, as the route guiding may access the same information that is used for the route finding at an earlier stage.
However, such techniques face certain restrictions. For example, a representation of the intersection in the road network graph may be simplified to a smaller or larger degree. For example, while the representation of the intersection in the road network graph may merely consist of four road segments and a connecting node, the real-world appearance of the intersection may be more sophisticated. For example, a plurality of driving lanes may exist which might have associated turning restrictions. Moreover, the real-world appearance of the intersection may have considerable extensions, i.e., the intersection may cover a significant area. In contrast, when modelling an intersection merely by using road segments and nodes of the road network graph, the intersection may be a point feature. In such a scenario it is not possible, or possible only to a limited degree, to provide route guidance while the vehicle moves through the intersection. The route guidance may be of limited use to the driver of the vehicle. A considerable likelihood of not successfully following the planned route may result. Therefore, a need exists to provide advanced techniques for providing route guidance along a planned route. In particular, a need exists to provide the route guidance along the planned route at intersections in a detailed manner.